Fluorescent light fixtures, popular for their long life, low energy consumption, and high light output, are frequently used in situations where they are subjected to considerable mechanical shocks. As the fluorescent tube, which is the essential light-emitting element for such a fixture, is invariably made of glass and is normally of elongated cylindrical shape, protection of it presents more problems than protection of a simple glass-bulb envelope for an incandescent lamp fixture.
It is therefore known from German Pat. publication No. 1,589,330 to mount the fluorescent tube by means of elastomeric holding blocks in the recess of a fixture housing. This recess is then covered with a transparent lens which may be constituted as a diffuser. Such an arrangement is extremely effective in protecting the tube itself from being directly impacted from outside, and even from shocks which will be transmitted through the housing of the fixture to the bulb. Nonetheless it is still possible for shock waves transmitted through the air to be effective on the fluorescent tube and, in extreme situations, to break this tube. It is, in fact, even possible for the tube to be damaged beyond use without the light fixture housing or its lamp being damaged whatsoever. It has also been suggested in German Pat. publication No. 2,529,286 to dispense entirely with a light-fixture housing, and to simply mount the tube itself in a protective sleeve. The sleeve can in fact be formed as an elastomeric mass covered with a dense skin, all of course of transparent material. Such an arrangement has proven relative effective in protecting the tube against low-amplitude shocks, but is almost completely ineffective when the fixture is struck a substantial blow.